Author Topic: Is it possible to break apart cloud renders?  (Read 2159 times)

Offline badamsfx

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Is it possible to break apart cloud renders?
« on: November 20, 2014, 03:50:26 AM »
Hi All, I am trying to separate a cloud render into different layers like fg, mid, and bg but am having no luck. I want each layer to affect the lighting of the other layers but be broken out into its own image for later compositing. I tried adding a Render_layer node to the Render node and then putting each set of cloud generating nodes into its own group and then referencing each group in the Object group lines in the Render_layers node but that didn't work, in fact the clouds disappeared from the render. I was hoping to be able to render them all at the same time but even if I have to do each one as an individual render I would be fine with that as long as they still interact with each other. The clouds are set up as volumetrics so is the problem that the Object group categories only work with hard geometry and not volumes? I'm not sure how else to approach this.

Offline Oshyan

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Re: Is it possible to break apart cloud renders?
« Reply #1 on: November 20, 2014, 04:10:12 AM »
Yes, exactly, the object groups are literally for objects only, they do not work for any other shaders or non-object elements. You can find documentation on the render layers and elements system here:
http://planetside.co.uk/wiki/index.php?title=Render_Layers_and_Render_Elements

To achieve what you want, I think you'll need to do separate renders. What you can do is turn off "Enable Primary" in each cloud layer that you want to hide, and that should keep its secondary effects (shadows, etc.), while making it invisible. So to render each layer separately, you'd turn off 2 and leave 1 enabled (in the case of foreground, midground, and background). But you would of course need to define your fore, mid, background cloud areas *in separate cloud layers* for that to work.

- Oshyan

Offline badamsfx

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Re: Is it possible to break apart cloud renders?
« Reply #2 on: November 24, 2014, 09:30:52 PM »
Awesome, this is exactly what I needed and works great. Thanks Oshyan. Any chance that Terragen will someday be able to export cloud data in vdb or field 3D format?

Offline Oshyan

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Re: Is it possible to break apart cloud renders?
« Reply #3 on: November 24, 2014, 09:59:14 PM »
It's possible, but we have no specific plans to do so yet. We are more likely to support Deep Compositing EXR output in the future however.

- Oshyan

Offline Matt

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Re: Is it possible to break apart cloud renders?
« Reply #4 on: November 26, 2014, 01:47:17 AM »
Another way to do this is to set near and far clipping distances in the Render Layer. In some cases that might be an easier way to go.

There is a way to get object groups to work with cloud layer - you would attach the clouds to separate planet objects and then use object groups to select the planets.

Matt
« Last Edit: November 26, 2014, 01:50:24 AM by Matt »
Just because milk is white doesn't mean that clouds are made of milk.

Offline goldfarb

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Re: Is it possible to break apart cloud renders?
« Reply #5 on: November 26, 2014, 03:35:21 PM »
It's possible, but we have no specific plans to do so yet. We are more likely to support Deep Compositing EXR output in the future however.

- Oshyan

interesting...
I'd strongly suggest VDB export (and import ;) ) first...
deep compositing, while very cool, isn't something that many people/studios will (or can) use in the near future, but VDB is quickly becoming the standard and it would be amazing to be able to import volumes for things like fog and FX type stuff...and then just deal with holdouts the way we've been doing it all along...then have deep compositing come along later...

just my 0.02...
--
Michael Goldfarb | Senior Technical Director | SideFX | Toronto | Canada

Offline Oshyan

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Re: Is it possible to break apart cloud renders?
« Reply #6 on: November 26, 2014, 08:39:42 PM »
Good to hear that VDB is gaining traction. It's something we're also looking at.

- Oshyan

Offline badamsfx

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Re: Is it possible to break apart cloud renders?
« Reply #7 on: December 10, 2014, 01:42:59 AM »
Another way to do this is to set near and far clipping distances in the Render Layer. In some cases that might be an easier way to go.

I tried that initially but it gets tricky because I'm rendering with a spherical camera to make skydomes. I would have to make circular clipping planes which someone showed me how to set up but it's harder to control than just putting layers of clouds at different altitudes.

There is a way to get object groups to work with cloud layer - you would attach the clouds to separate planet objects and then use object groups to select the planets.

Matt

I will have to look into this. Thanks!

Offline badamsfx

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Re: Is it possible to break apart cloud renders?
« Reply #8 on: December 10, 2014, 02:20:58 AM »
Another question regarding render layers. The cloud rgb pass renders out fine and when I add the cloud and sky's rgb together the image exactly matches the "all in one" render. When I look at the cloud alpha pass though it has color in the various channels. Which channel accurately represents the cloud's alpha? In my particular render the red channel has the most information in it. Or should I do a lumakey of the alpha image? Traditionally the alpha would just be a grayscale image.

Offline Oshyan

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Re: Is it possible to break apart cloud renders?
« Reply #9 on: December 10, 2014, 05:40:26 AM »
TG does alpha for each channel respectively. In other words it is the appropriate level of transparency for each of the Red, Green, and Blue channels. I think you'd want to mask each channel by its corresponding mask if possible, otherwise I believe you'd merge them to operate as a single mask on an RGB image.

- Oshyan

Offline dorianvan

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Re: Is it possible to break apart cloud renders?
« Reply #10 on: May 30, 2017, 06:59:55 PM »
But you would of course need to define your fore, mid, background cloud areas *in separate cloud layers* for that to work.

- Oshyan

I know this is an older post, but I hope still relevant information. I need some help "extracting" a cloud for post comp. I want to add png people in between a pure render (without cloud) and a low cloud layer. That way the people will get less distinct the more "in the cloud" they are. So I understand to uncheck Enable primary to get the shadow but no clouds, but what do I do with the rest? Something in the Render layer I'm guessing. Do you mean to make the Object group 1 to Atmosphere? Then what? Hope you can step me through this, thanks.

I tried the second planet thing, but I had nothing to plug the cloud layers in to. It only had an output plug.
-Dorian

Offline Matt

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Re: Is it possible to break apart cloud renders?
« Reply #11 on: May 30, 2017, 07:27:40 PM »
I tried the second planet thing, but I had nothing to plug the cloud layers in to. It only had an output plug.

New planets by default contain an internal network of nodes, and because they are connected internally the plugs don't show on the outside until you connect them to something on the outside. But if you simply duplicate the first planet you'll have a planet with external plugs.
Just because milk is white doesn't mean that clouds are made of milk.

Offline Matt

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Re: Is it possible to break apart cloud renders?
« Reply #12 on: May 30, 2017, 07:36:19 PM »
I know this is an older post, but I hope still relevant information. I need some help "extracting" a cloud for post comp. I want to add png people in between a pure render (without cloud) and a low cloud layer. That way the people will get less distinct the more "in the cloud" they are. So I understand to uncheck Enable primary to get the shadow but no clouds, but what do I do with the rest? Something in the Render layer I'm guessing. Do you mean to make the Object group 1 to Atmosphere? Then what? Hope you can step me through this, thanks.

If you already have one render with the cloud and another render where it's invisible, perhaps you could comp the people over each render and then simply blend between the two layers? You could eyeball the blend, or use a depth map of the people to control it.

Of course you'll save render time if the cloud render is just the cloud without the rest of the scene (by using a Render Layer to control visibility), but it won't necessarily give you better results than just blending between the with-cloud and without-cloud renders.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Offline dorianvan

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Re: Is it possible to break apart cloud renders?
« Reply #13 on: May 30, 2017, 08:18:12 PM »
Thanks Matt, I was wondering if a z-depth pass would help somehow. Not sure how though. Quickest option sounds like rendering the cloud separate with a different planet. The question remains however, what's the best way to set that up? Render Layer? Settings? Also, I assume I need a new cache for each part, right (with cloud/without)?
-Dorian

Offline dorianvan

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Re: Is it possible to break apart cloud renders?
« Reply #14 on: June 01, 2017, 05:48:10 PM »
I created a new planet, turned off the old one, and only had the cloud plugged into it. Created a new group called Planet Test and put the new planet in it. Then in the Render Layer, I put the planet test in Object group 1 and made it Visible. Render Elements has Cloud things checked. Nothing but black for everything. Am I doing something wrong? I just want to export only clouds.
« Last Edit: June 01, 2017, 08:23:27 PM by dorianvan »
-Dorian